Rear End Sag Mystery
 

I have a 2004 H2. Only 25k miles.

It is driven daily and parked about 8pm. About once a week when I go out in the morning the rear end is sagging. Kind of weird that it's only once a week. I took it to my local dealer and they couldn't find any leaks. Any thought? Thank you.

Air bags probably have some cracks in them. Air bags are relatively cheap and easy to replace.

yep they dry rot & leak air, both of my H2's did the same , depending where the air bag is (how inflated or deflated) when you shut the truck off , if may or may not leak, if I hit the height control button & raise it up , leave it overnight .. no leaks , try that or just get under the truck with a spray bottle of soapy water mix & spray the crease/roll & you should find the leak pretty easy

Thank you so much for the responses. It is greatly appreciated.

After reading here I also figured it was the airbags. But I took it to my local dealer and he checked them out. He said they look fine. No leaks. I will crawl under it and take a look for myself.

I just thought it strange that it only happens once every week or two. But it is driven everyday.

mine did the same thing, funny thing , I just bought an '06 a couple weeks ago, & when I was looking at it , I told the owner his air bags were leaking... he said no way & the dealer just bent him over for a 2k + bill for new dual compressor, , new air lines & sensors... well I actually fixed the problem with a $125 air bag.. that was the root of the problem, you will eventually burn up the compressor try to inflate defective air springs..

Is it hard to do the airbags myself. I'm not very mechanical.

No , it's easy, there's a couple you tube videos with step by step instructions , the hardest part is pulling the air line off

Ok. Thank you. I will look for the videos. How long should it take me to do both?

I wanted to bump this and update to hopefully get more advice....

I crawled under it this week. The airbags look fine. No cracks or anything.

The truck was driven last night until 10pm. Got up this morning at 6am and it looked fine. Looked out at 7am and the back was dragging.

So it sat all night and it was fine. Then within an hour it was sagging. And it only does this once a week or so.......

Perhaps your leak becomes more severe after a certain level of sag. So it starts out slow, and when the air bags reach a certain compression, the leak opens up and releases air at a faster rate. Next time, check for leaks when it's sagging.
If you get really fed up with your air suspension, it's also easy to convert to rear springs.

Maybe. I'm just wondering if it could be an airline or the sensor. Is there a release valve that let's sit out of the airbags when weight is added or a sensor that tells them when to let air out?

Where can I get the air bags? Any recommendations? What do they cost? Maybe I will replace them and see what happens.

No.11 is airbag.

2004 Hummer H2 Parts - GM Parts Online - GM Parts Direct

Re read my post.... change out the air bags, It doesn't matter if your h2 has 20k or 200k, fact of the matter is their 10 years old & dry rotted.. Visual inspection is useless, spray them with soapy water to check for leaks.. even then it might not show up... imo for under $300 (new bags) & 1 hour of your time you can be done with it

Yes. I think I agree with you. I just wanted to be sure.

Should I go to my local auto parts store to order the airbags or is there somewhere else I shoukd go? Thank you.

Thank you. Is this the best place to order them or should I go to my local auto parts store?

You won't find them at your local auto parts store, I would use gm direct or your local gm dealer

Great. Thanks to everyone for all of the help.

I just ordered them online via the above link. Thanks for the link. That made it easy.

I just watched the video on YouTube. Is it really that easy. No tools needed. Jack it up. Cut the bag. Twist it off. Pop the airline off. Any pointers? The airline has me a little worried.

Check the airlines too. Mine were leaking too

Bump. Just tracked the airbags. They will be here in 2 days. Any tips on installation? My main concern after watching the video is getting the airline off and on..... Any suggestions or instructions? Thank you.

This pretty much covers it, just hold down the fittings & pull with all you got .. It will come off

It looks too easy. I feel like something gas to go wrong. Lol.
Seeing the video makes me wonder how the air fitting will go back on and seal. Is that prone to leaking? Just pushing it on doesn't seem like it would seal very well.

they do make it look easy... the hardest part for sure is removing the old bag, piece of cake after that , you HAVE to be very careful not to damage the air line that attaches to the top air fitting, or yes it will leak, I ran into this & had to splice in a new section of air line, just take your time & you should be good

Great. Thank you for all of the help. It is greatly appreciated.

UPS tracking said my airbags will be here on Monday.

New information. We had new tires put on it yesterday. They had to jack it up. Brought it home. It was sagging right away. Parked it today and it was sagging right away.

Maybe jacking it up finished off the airbags??? Funny I still can't see any cracks. They look new.

yes, I would bet when it was on the hoist it stretched the bags & made the leaks worse, keep us posted on how your install goes

Well I got both airbags installed over the weekend. It was pretty easy. I agree the hardest part was the airlines.

So far it has been 4 days and no sag in the morning. I think that was it. I will update in a few more days.

Thanks to everyone for the help. My dealer wanted $800 to do the airbags. With the help here I did it for $250 and 30 minutes of labor. You guys are the greatest. Thanks again.

That's Great! I agree... I count not afford any of my toys if I had to pay someone every time an issue arose!!

Update. I have noticed the last few days that it might have a small sag after sitting all night. I went out this morning and measured from the ground to the top of the wheel well. 41". Then I started it and let it air up. It went up 2 inches. Is that normal or do I still have a problem somewhere?

Also according to my air gauge after sitting all night the air is down to the bottom of the gauge. It has always done this. Is this normal?

The air suspension provides a 2" light when raised to its highest if I remember correctly.

So it would be normal to have it down 2 inches.?

no... it should not drop at all overnight.. after I installed new air bags on both of my H2s, the height would stay the same, I would check the fittings on top of the bags & make sure they sealed up ,

Ok. I will check the fittings and post my findings.

I checked the fittings. Everything seemed fine.

Consistently about 2 inches low everyday. Any ideas what it could be? There has to be a one way check valve. Maybe it is leaking. Leveling valve?

Hello y'all!!!
Were new here and we have a 05 h2 that has the sagging rearend mystery!
We've been readin on here and this thread is awesome.
The chevy dealer told us the compressor was bad and it was a1200 part!
I didn
t think it was right because our h2 pumps right back up when we turn it on and drive it. Then it used to leak overnight, now after the chevy place lifted it it leaks down right after its turned off.
So this thread is spot on.
Y'all mentioned if it's not fixed quick the compressor will go bad.
How do we know when the compressor is bad?
I would assume the back of the car would not pump back up and continue to sag even with engine running.
Would that assumption be accurate?


Cool place y'all, I cant wait to read more!!!

Correct

Could temp changes be having an effect on the sag?

Is it dangerous driving hummer at freeway speeds while back end suspension is low due to leaking air bag and compressor turned off.